Calutron ion source



24,1959 7 w. M. BIIQOBECK I 2,875,339

CALUTRON ION SOURCE Filed March "1, 1946 2 Sheets-Sheet 1 INVENTOR. WILL/AM M. BROBECK mam Feb. 254, was

w. M. BROBECK CALUTRON ION SOURCE 2 Sheets-Sheet 2 Filed March 1, 1946 INVENTOR. W/LLl/JMM BROBECK ilnited States Patent CALUTRON ION SOURCE William M. Brobeck, Berkeley, Calif, assignor to the United States of America as represented by the United States Atomic Energy Commission Application March 1, 1946, Serial No. 651,281

7 Claims. Cl. 250-419 The invention relates to means especially effective to 2,875,339 Patented Feb. '24, 1 959 the above-identified patent of Lawrence, a brief review produce ions and particularly to an ion producing means of the nature referred to as a calutron. Such a device is disclosed more particularly in U. S. Patent No. 2,709,- 222 which issued May, 24, 1955 to Ernest 0. Lawrence. Several forms of calutron are disclosed in the Lawrence patent and the one to which the present invention most closely appertains is especially disclosed in Figures 3 to 5 of that case.

Some ionizing mechanisms, particularly thosev of the calutron type, such as disclosed in the above-identified Lawrence patent and in my previous U. S. Patent No. 2,736,808 which issued February 28, -1956, generally utilizeas a means for producing ions an electric arc struck between a cathode and an anode with the length of the are substantially parallel to a magnetic field within which the structure operates. The material to be ionized-usually in vapor or gasv form, is caused to flow to the vicinity of or through the arc and collisions between the arc electrons and the molecules of the vapor induce the formation of a number of ions that are subsequently Withdrawn from the 'arc orits vicinity by means of a suitable structure such as an accelerating electrode. It is quite important in the production of ions by this means that the are be operated at as steady a value as feasible and "that it be as uniformas possible throughoutits length.

ment serving as a cathode for the are be somewhat protected from the effects of non-ionized particles escaping from the ionizing mechanism.

It is therefore an object of my invention to provide means for improving the arc structure and its surroundings in a device in the nature of a calutron.

Another object (of the-:invention is to .provide means for facilitating uniformity of operation in an ionizing arc. An additional object of the invention is to provide means for protecting the filament in an ionizing arc.

A further object of the invention is in general to improve arc ionizing mechanisms.

A still further object of the invention is in general to improve mechanisms of the calutron type.

Other objects together with the foregoing are attained by the embodiment of the invention described in the following description and illustrated in the accompany ing drawings, in which:

Figure l is a fragmentary view of a portion, particularly the source unit, of a calutron, a portion of the figure being disclosed in cross-section on a vertical, median plane and portions of the figure being broken away to reduce its size.

Fig. 2 is an isometric perspective of the source mechanism and its immediately adjacent structure as illustrated in Fig. 1 but with portions being broken away to disclose the interior arrangement.

of that structure will suflice for an understanding of the present development and is given in connection with Fig. l.

v In a calutron there is provided a volume 6 permeated by a uniform or homogeneous magnetic field established between the upper pole 7 and the lower pole 8 of an electromagnet. Disposed between the poles 7 and 8 and situated within the magnetic field is a tank or vessel 9 enclosing'a chamber 11 connected to suitable pumping mechanism such as a diffusion pump (not shown) eifective normally to evacuate the chamber 11 to a pressure of approximately 10- mm. of mercury. The tank 9 in cludes a top wall 12, a bottom wall 13, and a face plate 14.

Secured removably to the face plate is an insulator 16 serving also as a support for a mounting and adjusting mechanism 17 not described in detail herein as its detailed functioning -is not of consequence in connection with the present invention. The structure 17, however, acts as a support for a mounting stem 18 of a source block 19. A number of conductors 21 and leads 22 included inthe structure 17 pass with vacuum tightness from the atmosphere into the interior of the chamber 11. The stem 18 is preferably related to the source block 19 by a terminal flange 26 and'suitable fastenings 27 so that while some thermal insulation is afforded there is nevertheless goodelectrical contact.

The source block 19 is at its inner end provided with a heater cavity 28 closed'by a disk 29 at its upper end and receiving through its lower end an electric coil heater 31 mounted on an insulating core 32. The heater coil is connected to a pair of leads 33 and 34 one being joined to one end of the conductor 22 and the other beingconnecteclto the block or flange 26. Upon the imposition of a suitable potential difference between the conductors 18 and 22 the heater 31 is effective to increase the temperatu're of the. block 19. The source block preferably is of metal so that heat from the coil'31 is generally conducted in a uniform fashion to a charge cavity 36 formed within the block 19. The charge cavity extendsnearly through the under side of the block and entirely through the top face 37 thereof.

Establishing communication between the cavity 36 and theexterior face 38 of the-block 19 is a 'gas' passage 39 defined by a pair of parallel planar walls 41 and 42 so that the passage is a straight one extending from within the block to the outside thereof and thus merging not only with the face 38 but also with the adjacent face 37. When charge material is placed in the cavity 36 it is heated and evolves gas or vapor that travels from the cavity 36 rather uniformly through the passage 39 to the exterior of the block.

To close the cavity 36 and a part of the passage 39 there is provided on the face 37 in abutment therewith a plate 43 fastened to the block 19 by suitable screws 44and effective to seal one end of the cavity and one end of the passage. The plate 43 preferably extends beyond the face 38 and overhangs the edge of the block 19. The plate is provided, in registry with the passage 39, with an aperture 46 preferably symmetrically disposed with respect to the passage. r

Adjacent the block 19and overlying the plate 43 is a filament 47 held by grips 48 and 49 at the ends of filament .largedplate 53 overlying the-filament 47 to substantially the same extent or to a slightly greater extent than the 'plate 43 underlies the filament.

When a correct potential difference is established between the filament 47 and the block 19 an arclis struck betweenthe filament and the block. The are passes throughthe-aperture 46 extends down between the walls 41 and 42 and strikes on the bottom 54 of the passageway 39 which therefore serves as an anode. This action is facilitated as the filament and the passage are the same shape, but the filament is narrower than the passage. 7

Since the arct traverses substantially the entire length of the straight, parallel-walled passage 39, substantially all of the gas that flows from the gas chamber must, pass through the arc and since the arc is confined between these walls it is maintained relatively uniform throughout its entire length. As the emitting portion of the filament varies at random during operation, the arc is still within a uniform passage so that no variation in ion production results. The continued uniform operation of the filament is fostered by the projecting plate 43, since non-ionized gas flowing from the passage 39 does not directly impinge upon nor bombard the filament.

Thus, in accordance with the invention there is provided an improved structure for the production of a large amount of ionization in a calutron with a relatively uniform are and with extended filament life. It is furthermore the case that a variable position of the are within the passage 39 toward or away from the block face 38 during operation corresponding with variation in the emitting portion of the filament 47, does not substantially affect the general positioning of the arc in a direction parallel to the plane of the face 38. In this fashion great stability of operation is assured and a general improvement in calutron operation is attained.

What is claimed is:

1. A calutron ion producing mechanism comprising a source block including a gas chamber and having a straight parallel-walled gas passage from said gas chamber to the edge of said source block, a filament overlying said passage and having a straight portion parallel to the length of said passage, the width of said filament being less than the width of said passage, and means for including said filament and said block in an electric arc circuit.

2. A calutron ion producing mechanism comprising a source block including a gas chamber and having a straight a gas passage extending from said gas chamber to the edge of said source block, a plate overlying and closing a part of said passage, said plate having an aperture therein in line with said passage, a filament overlying said passage and said aperture, and means for including said filament and said block in an electric arc circuit.

3. A calutron ion producing mechanism comprising a source block including a gas chamber and a gas passage open to two adjacent faces of said block, a plate overlying one end of said chamber and of said passage in abutment with one of said faces, said plate having an aperture therein in alignment with said passage, a filament overlying said aperture, and means for including said filament and said block in an electric arc circuit.

4. A calutron ion producing mechanism comprising a source block including a gas chamber and a gas passage extending from said gas chamber to two adjacent faces of said source block, a plate overlying said passage and abutting one of said faces and extending beyond the other face of said block, said plate having an aperture therein in line with said passage, a filament overlying said aperture, and means for including said filament and said block in an electric arc circuit.

5. A calutron ion producing mechanism comprising a source block including an open ended gas chamber, an elongated aperture extending from the open-end of said block substantially to the depth of said chamber and com- ;municating betweensaid chamber and 'a wall of said block adjacent said open end, means supporting a filament over said open end, a'straight portion of said filament being disposed parallel to the open end of said communicating aperture and'having a width less than said aperture, and means for including said filament a'ndsaid block in an electric arc circuit.

6. A calutron ion producing mechanism comprising a source block including an open ended gas chamber, an

elongated aperture extending from the open end of said block substantially to the depth of said chamber and communicating between said chamber and a wall of said block adjacent said open end, a plate overlying the open end ofsaid block and communicating aperture, said plate having an opening therein in alignment with said communicating aperture, means supporting a filament over said plate and-spaced apart therefrom, a straight portion of said filament being disposed parallel tothe open end of said communicating aperture and having a width less than said aperture, and means for including'said filament and said block in an electric arc circuit.

7. A calutron ion producing mechanism comprising a source block including a gas chamber and a gas passage open to two adjacent faces of said block, a plate overlying one end of said chamber and of said passage in abutment with one of said faces, said plate having an aperture therein in alignment with said :passage, said aperture having a dimension greater than said passage, a filament overlying said aperture and having awidth dimension less than the width of'said passage, and means for including said filament and said block inan electric arc circuit.

Bleak'n'ey Nov. 12, 1940 Washburn July 12, 1949 

